Control apparatus



Sept. 2, 1952 F. R. FITZGERALD CONTROL APPARATUS 2 SHEETS-SHEET l Filed Sept. 2, 1948 Bnoentor m w.m GM U m H K M m f Sgpt. 2, 1952 F. R. FITZGERALD 2,609,133

I CONTROL APPARATUS Filed Sept. 2, 1948 2- SHEETS-SHEET 2 298 I 259 w 75 3p1ventor Ffifi/Ylf IT. F/TZ GEE/71D Gttomeg Patented Sept. 2, 1952 UNITED STATES PATENT OFFICE Frank R. Fitzgerald, El Monte, cane, assignor to "Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application September 2, 1948, Serial No. 47,452

13 Claims. 1

The present invention relates to thecontrol of air conditioning apparatus for a plurality of zones in response to the average requirements for 'those'zones.

In large buildings having a plurality of zones which have somewhat difierent heating or cooling requirements, a double duct air conditioning system is frequently used. In this system, one of the ducts carries relatively hot air and the other ductrelati'vely cold air, each of the ducts being suitably connected through mixing dampers with each of the zones, the mixing dampers being controlled by individual zone thermostats. With this arrangement, if a zone is relatively cool, the mixing damper will be adjusted to reduce the supply of cold air and increase the supply of hot air and, obviously, reduce the supply of hot air and increase the flow of cold air when the zone is relatively warm. -If the hot air is hot enough to meet the extreme heating load and the cold air cool enough to ineet the extreme cooling load, it is apparent that the dampers must, at times, operate near their fully closed position and thus become diflicult to control because of the well known iiow characteristics of dampers. Also, sincesuch a system must provide for the total required'air volume traversing each ductseparately at extreme heating load and at extreme cooling load, respectively, each duct must be sized to carry the total volume of air. With the present invention, the load is better distributed between the duo aence they may be made somewhat smaller, with a consequent saving 'in' cost. Further, because a system such as described tends to circulate b'e'th hotter and colder airthan actually needed, operating economy is sacrificed to flexibility. In the present invention, the air is tempered no in e than necessary, resulting in savings in both --if1itial and operatingcosts and an improvement in'ontrol.

It is thus an object of the present invention to improve the double duct system of air conditioning by making it easier to control, more economi'cal to operate, and in some instances more economical to install. i

It is a further object to provide control apparatus for a double duct air conditioning system which requires no more heating or cooling of the air delivered than is necessary to meet the zone needs.

It is another object of this invention to provide control apparatus for a double duct air conditioning system eirectiv'e to vary the temperature of the air delivered by said ducts in response to difierences in air velocity in said ducts.

. passing through said ducts.

It is a further object to provide control apparatus for a double duct air conditioning system wherein a device responsive to temperature in each'duct controls its respective temperature changing apparatus and wherein said devices may be reset to control todifierent temperature values in response to the different velocities of air passing through said ducts. 7

It is also an objectto provide a control system for a double duct air conditioning system wherein the temperatures of the delivered air are normally determined by the heating or cooling requirements of the zone but wherein said delivered air temperatures may also be varied in response to relative humidity.

It is an additional object to provide control apparatus for a double duct air conditioning system comprising air velocity responsive means for determining the system load.

These and .other objects will appear upon a study of the following specification and drawings wherein: Y V

Figure 1 is a schematic view of a preferred form of the present invention.

Figure 2 is a schematic view of a modification of part of the apparatus of Figure 1.

Figure 3 is a schematic View similar to Figure 2 showing a further modification of the apparatus of Figure 1.

Figure 3A is a schematic view of a modified arrangement of the bellows devices of Figure 3.

Figure 4 is a schematic view of a modification of Figure 1 wherein electrical apparatus isused instead of the pneumatic apparatus of the previous views.

Figure 5 is a schematic view of a differential velocity apparatus for the system of Figure 1 using swinging vanes.

Figured is a diagrammatic view of an electrical system similar to the system of Figure l.

Figure"? is a schematic view of modified arrangement for the system of Fi u 5 wherein velocity is sensed in only one duct.

In Figure 1, rooms or zones l0, l2, and I4, as well as other zones, not shown, are supplied with tempered air by a double duct air distributing system comprising a warm air duct l6 and a cold air duct I8. Branch ducts l9 and. 20, controlled by mixing dampers 2|, are connected to ducts I6 and I8, respectively, the mixing dampers 2| being so constructed that duct l9'is opened as duct is closed and vice versa. Dampers 2| are operated by a thermostatic device 22 comprising a spring 23 and an expansible bellows 24, the force exerted by the spring tending to move dampers 2| in a direction to open duct I9 and close duct 20, and the expansive force of bellows 24 tending to adjust dampers 2| in a direction to close duct l9 and open duct 29. Obviously, thermostatic device 22 is illustrative only and dampers 2| may be manually operated or may be operated by either a pneumatic or an electric motor controlled by a suitable thermostat. Branch ducts 21 and 28, controlled by mixing dampers 29, are connected to ducts l5 and I8, respectively, and dampers 29 are operated by a thermostatic device 3|] similar to 22 just described. Likewise, branch ducts 3| and 32, controlled by mixing dampers 33, are connected to ducts l6 and I8, respectively, and damper operating thermostatic device 34 is similar to devices 22 and 30.

Air is supplied to ducts l6 and I8 by a blower 36, the intake of which is connected to a return air duct 31 and an outside or fresh air duct 38. While dampers are generally provided for varying the proportion of fresh air and return air, such dampers are not shown because of space limitations and because they form no essential part of this invention but it is obvious that they may be used if desired. The air delivered through duct l5 may be heated by a suitable heat exchanger or steam coil disposed in said duct and supplied with steam through pipe 4| under the control of a normally open throttling valve 42 having a spring 43 for urging the movable valve member in an opening direction and having a pneumatic motor 44 for opposing the spring 43 and closing the valve. Likewise, the air delivered through duct l8 may be cooled by a suitable heat exchanger or cooling coil 45 supplied with chilled brine or the like from a source, not shown, through. pipe 46 under the control of a normally closed throttle valve 41, valve 41 including a spring 48 for urging the movable valve member to a closed position and pneumatic motor 49 being arranged to oppose spring 48 and open the valve. Obviously, any other conventional and controllable heating and cooling apparatus may be substituted for that above described.

The pressure applied to motor 44 of valve 42 is regulated by a submaster type thermostat 5| having its stem portion 52 arranged in duct I6 for responding to the temperature of the air in said duct downstream from coil 4|), thermostat 5| being connected to motor 44 by tube 53. Thermostat 5| receives its air supply for a suitable source such as 54 through pipe 55 and tube 56. The pressure imposed on motor 49 of valve 41 is likewise controlled by submaster thermostat 51, identical with 5|, and having an insertion stem portion 58 extending into duct I8 and responding to the temperature of the air in said duct downstream from cooling coil 45. Thermostat 51, and this description applies equally well to 5|, comprises a tube portion 59 having a relatively high temperature coefiicient of expansion and a relatively non-expansible rod portion 60 anchored to the bottom of the tube. Rod 60 is connected through suitable knife edge contacts to lever 6| pivoted on knife edge 52 and urged in a counterclockwise direction by a tension spring 53. As thus arranged, upon a temperature rise, tube 59 expands and moves rod 60 in a direction to pivot lever 6| in a clockwise direction whereas, upon a temperature fall, tube 59 contracts and permits spring 63 to rotate lever 6| in a counterclockwise direction. The other end of spring 63 is connected to lever 64 pivoted at 55 and bearing against the operating stem of valve unit 66 and a set-up bellows 51. Valve unit 66 is of a conventional sort and is so arranged that when lever 64 is in a neutral position, there is no change in branch line pressure in tube 58 connecting valve unit 66 to motor 49. However, if lever 54 be rotated in a clockwise direction, thus moving the operating stem of the valve inward, the pressure in branch 68 is increased whereas, if lever 64 be moved in a counterclockwise direction, the pressure in branch 58 will be diminished. Set-up bellows B1 is arranged to oppose spring 63 by an amount depending upon the pressure imposed on it through tube 69, a relatively high pressure in bellows 51 tending to move lever 64 in a counterclockwise direction to thus bleed the pressure in branch 68 to zero hence, in effect, to shift the control point of the instrument upwardly by requiring a greater elongation of tube 59 to restore lever 64 to its neutral position, the greater elongation of tube 59 resulting in a clockwise movement of lever GI and an increasing of the tension of spring 63. The valve unit 66 of device 51 obtains its supply of air from source 54 through pipe 55 and tube 10. For a fuller description of submaster thermostats 5| and 51, reference ismade to Patent 2,363,595, issued to F. D. J oesting, November 28, 1944. Obviously, any other suitable thermostats subject to resetting or remote adjustment in a manner similar to these thermostats can be substituted for devices 5| and 51.

The resetting, or the remote adjustment, of thermostats 5| and 51 is accomplished by a difierential pressure responsive device 12. Device 12 comprises a pair of inverteed cup-like members 13 and 14 attached to a pivoted beam 15 and arranged with their lower and open ends immersed in oil 16 in a suitable receptacle 11. A pressure sensing conduit 18 is arranged with one end opening into conduit l6 and its other end extended above the surface of oil 16 under cup-like member 13, conduit 19 being similar to 18 but having one end opening into conduit I8 and its other end terminating above the surface of oil 16 under cup-like member 14. As thus arranged, the static pressure in conduit H5 is communicated to the under side of cup 13 and the static pressure inconduit I8 is communicated to the underside of cup 14, and any difierence in these pressures will tend to cause a pivoting of lever 15. An upwardly extending member is attached to lever 15 and is arranged to contact valve plate 8| pivoted at 82 and spring urged against a nozzle 83 to normally close said nozzle. An adjustable spring 1| is provided for biasing extension member 80 in a direction to move valve plate 8| away from nozzle 83, this spring having slightly greater strength than the spring holding the valve plate 8| against the nozzle, so that plate 8|, when the pressures under 13 and 14 are equal, will be held in a 5 partially open position. Then, if the pressure in 13 is slightly above: that T111 .14 the nozzle 83 will be completely opened whereas, if-the pressure in 14 exceeds that in 13, the nozzle 83 can be completely closed by its spring." Nozzle 33 and its coacting nozzle plate 'iiI -controls th'c bleeding of air, from tube 85, the air being obtained from source 54 through pipe 551and a .restriction 84. Tube 85 also connects with tube 56 leading to the reset bellows of thermostat 5| and. to tube 81, which may connect with tube 69 but whichis shown connected to a relay 88. As thus arranged, a restricted quantity o f air is permitted to pass through restrictor 84 and may be bled away through nozzle 03, when the nozzle plate is in a remote. position, thereby causing a minimum pressure in the tubing downstream from the restrictor 84 and causing a minimum pressure in the set'up bellows of thermostats 5i and 51. However, if plate 8I seals off nozzle 33, the air pressure builds up in the connecting tubing downstream from the restrictor until it' Rather than connecting tube 81 to tube tail and thus changing the'pressure in bellows 61 in accordance with device 12, a diverting relay as is interposed for a purpose which will appear. Diverting relay 88 comprises a first pressure chamber 83 bounded in part by a flexible diaphragm 9a. A similar pressurechamber 9i including a fiexiblediaphragm 92 is arranged oppositely to the first named pressure chamber, with a connecting member 93 being arranged between the diaphragms 9B and 92. Member 93 is connected to open valve 94 in valve chamber 95 when it is shifted downwardly and to. open valve 95 in valve chamber 91 when it is shifted upwardly. Valves 9 and 96 control the air passages from their respective valve chambers into chamber '98, to which tube 69 is connected. Tube 81 is connected to pressure chamber 89. and a branch tube IIiI also connects 81 to valve chamber 91. Tubes I92 and l 03 connect valve chamber 95' and pressure chamber 9| to nozzle lbs of humidity responsive device I05.

Humidity responsive device 105 also includes a conventional hair element I03 which'is attached to a pivoted lever I01,.lever I01 being urged in a clockwise direction bya spring I03. The lower extremity of lever I01 is arranged to engage plate I09, pivoted at I I and spring urged in a direction to close nozzle I04. Thus, when the relative humidity is relatively low, element I is contracted and lever I01 is rotated in a coun terclockwise direction to thus permit plat-e I09 to be pressed against nozzle I04 by its spring and prevent the bleeding of air from said nozzle. Air is supplied to tube I03 from source 54 through a tube H2 in which is located a restrictor H3. With this arrangement, when nozzle IM is closed, due to a relatively low humidity, full line pressure builds up in tubes I02 and I 03 and in chambers 95 and 9 I With a higher pressure in chamber SI than in 89, member 93 is shifted upwardly, valve 96 is opened and communication exists between tube 81, tube IIJI, chamber 98 and tube til, differential pressure responsive device 12 thus controlling the resetting of thermostat 51. However, when the relative humidity reaches a a relative sure in its bellows '61.

predetermined high value and nozzle [M is opened due to theext'ension ofelement I0 3, the pressure in chamber 91 is reduced and the pressure in chamber 89 may then exceed that in 9!. When the pre'ssurein chamber 89 exceeds that in chamber 9I, member 93 is shifted downwardly, closing valve 96 and opening valve 95 to thereby place tube 65 in communication with tube I03 through chamber 93 and valve es, thusplacing device I05 in control of theresetting of thermostat 51.

The design of the present system, as an example only, is, such that when outside temperature is F., temperature of the air supplied to the zones should be approximately 110, and when the outside temperature is 100, temperature of the air supplied in the zones should be approximately 55.

:In operation, it may be assumed that blower 3B is operating and is, circulating about onefourth fresh air and three-fourths return air through ducts I6 and I8 to the several zones including Ill, I2, I4. Thermostat 5I may be adjusted to control at a'temperatureof 23 with 100 set-up possible by its resetting bellows so that, with maximum pressure at its resetting bellows, it will control at 123. Thermostat 51 may be adjusted to control at 48 with a 50 set-up, so that it will control at 93 with a maximum pres- Difierential pressure responsive device 12 may be set to provide maxi mum set-up air pressure in tube 85 when conduit I6 is carrying 80 per cent of the total air volume being supplied by blower and minimum air pressure in tube t5 when conduit I8 is carrying 80 per cent of the total air volume. With the apparatus adjusted as described, and with relative humidity responsive device I05 adjusted to maintain its nozzle I04 closed at relative humidities under 60 per cent, it may next be assumed that equal air pressures exist in conduits I6 and I8, due to the average openings of dampers 2 i, as and 33 causing equal flows from the two conduits.

Under these conditions, as above discussed, it may be assumed that valve plate BI is slightly spaced from nozzle 83 so that the resulting pressure in tube 85, the resetting bellows of 5!, chamber 89 and bellows 61 is eight pounds per square inch. At this pressure, device 5i is reset to control at 73 and device 51 is also reset to control at 73. If the mixture of outside air and return air is below 73, then thermostat 5| controls valve 42 to permit steam flow through pipe AI and coil to heat the air and bring it to the desired 73. With the air passing through coil under 73 in temperature, tube 59 is relatively contracted so that lever 64 tends to be rotated in a counterclockwise direction, this direction of rotation being recognized as that which bleeds down the pressure in branch tube 68 leading from valve unit 66 to valve motor is, hence spring 48 is able to keep valve 41 closed. Therefore, although device 51 is adjusted to control at 73, the air to which it is exposed is at a lower temperature without any cooling, hence no further cooling is provided.

The relative humidity may be assumed to be lower than the 6-0 per cent for which device Hi5 is. set, hence nozzle I04 is closed, the full supply pressure in chamber 9| exceeds that (eight pounds per square inch) in 89 so that valve 96 is open to thereby place tube 81 in communication with tube 69 so that device 12 controls the resetting of device 51.

If the temperature should now fall in zones Is and. I4, the contraction of the bellows of devices 22 and 34 will cause a closing of branch conduits 20 and 32 and the wider opening of conduits I9 and 3|, to thus introduce'more heat. The 73 air in duct I6 does not possess much heat'ior raising the temperatures in the zones but the wider opening of branch ducts I9 and 3| leading from conduit I permits a freer flow of air from this conduit and thus a slight reduction in the pressure in said conduit. Further, the closing of ducts 20 and 32 causes added restriction to flow from duct I8 and thereby causes a slight increase in the pressure in said duct I8. As a result, the pressure in .cup I4 is increased above that in 13 thereby causing a counterclockwise rotation of lever I and a consequent closing movement of valve plate 8| toward nozzle 83. This causes the pressure in tube 85 to increase with a consequent increase in the pressure in the resetting bellows of devices 5| and 51. An increase in the resetting pressure of thermostat 5| causes it to control at a higher temperature hence it operates to decrease the pressure in branch conduit 53 to permit spring 43 to more widely open valve 42 and thereby increase the heat delivered to the air passing through coil 40. At the same time, the temperature at which device 51 controls is also increased but, as the controlling action amounts to a lowering of the branch pressure, and valve 41 was already closed due to the low branch pressure, this valve stays closed and there is no cooling provided."

Should the average zone temperature diminish sufiiciently, so that all the mixing dampers are adjusted to permit 80 per cent average flow of air from duct I6 and per cent average flow from duct I8, then the pressure difference in device IZ will be sufiicient to completely close nozzle 83, with a consequent maximum resetting of thermostats 5| and 51. At this point, device 5| will control valve 42 to require 123 air in duct I5 whereas device 51 will require cooling of the air in duct I8 to 98 F. As 98 is above the temperature of the air being delivered from blower 36, valve 41 remains closed. With the apparatus controlling as described the mixture of air supplied from conduits I6 and I8 will be not less than 110 when the heating is a maximum, thus meeting the design requirements without extreme positioning of the mixing dampers and without undue deviation of room temperatures.

Now, instead of zones I0, I2 and I4'falling in temperature, let it be assumed that they tend to be too warm. With the temperature in the zones above that desired, the devices 22, and 34 will operate to drive the dampers for ducts I9, 2! and 3| toward closed positions, at the same time opening the dampers for ducts 20, 28 and 32. The restricted flow from duct I5 and the free flow from duct I8 then causes the pressure in duct I6 to be higher than that in I8, resulting in lever 75 of device I2 being rotated in a clockwise direction. The clockwise rotation of lever 15 causes the extension 80 to push valve plate 3| away from nozzle 83 and thereby reduce the pressure in tube 85 and its connecting passages including the reset bellows of thermostats 5| and 51. As the pressure in tube 85 and the reset bellows goes below eight pounds per square inch, device 5| tends to control at a temperature below 73 as does device 51. However, assuming that the mixture of outside air and return air is approximately 73, and device 5| is set to control at a lower temperature. than 73, then it causes an increase in the pressure in branch 53 and motor 44 sufficient to close valve 42 for there is no need to heat the air in duct I6 if its temperature is already above the value at which the device 5| is set to control. Assuming that device 51 is now reset to control at a temperature of 65 and the air is at about 73, the reduced pressure in bellows 6! permits spring 63 to cause a clockwise movement of lever 64 and thus operate valve unit 66 to increase its branch pressure and thereby open valve 41. Opening valve 4'! permits cooling medium to flow through coil 45 and cool the air in duct I8, the cooler air flowing past thermostat 51 causing a contraction of tube 59, a counterclockwise movement of lever 6| and a decrease in the tension of spring 63 so that the thermostat reaches equilibrium when the air in duct I8 is at the desired temperature of 65. With the temperature of the air in duct I8 below the temperature value required in the zones I0, I2 and I4, the relatively cool air introduced through ducts 20, 28 and 32 may tend to lower the temperature in these zones whereupon the resulting contraction of the bellows 24, 30 and 34 again causes an adjustment of dampers 2|, 29 and 33 in a direction to restore uniform pressures in ducts I6 and I8, resulting in an increase in the set-up pressures for devices 5| and 51. Thus, when the average flow from duct I0, or the duct carrying the heated air, exceeds that from duct I8, or the duct carrying the cooler air, thermostat 5| is reset to control at a higher temperature value so that heat required by the zone can be supplied with a lesser flow of air. Likewise, when the flow from duct I8 is relatively greater than that from I6, device 5| is reset to call for less heat and. device 5| is reset to require cooling of the air passing through duct I8. Should the average zone temperature rise sufliciently to cause per cent flow of air from duct I8 and 20 per cent flow of air from duct I6, device I2 will cause a minimum set-up of thermostats 5| and 51'. Device 51 will then control at 48 and the resultant temperature of the air mixture supplied to the zones will not be above 55 when the cooling load is at a maximum, thus satisfying design requirements without extreme positioning of the mixing dampers and without undue deviation of zone temperatures.

In the description so far, it has been assumed that the relative humidity has been below the upper limit of 60 per cent for which device I05 is adjusted. However, if the relative humidity should now exceed the value for which device I 05 is adjusted, the extension of element I05 permits an opening of nozzle I04 in a manner previously described. Opening of nozzle I04 causes a reduction in pressure in chamber 9| so that its pressure tends to become less than that in chamber 89. When this happens, valve 96 is closed and valve 94 opens, as before described, and tube 69 is connected to tube I03 through chamber 98, valve 94, chamber 95 and tube I02 so that the pressure in set-up bellows 3? depends upon humidity responsive device I05. The reduction in pressure in tube 69 and bellows 61, caused by the open nozzle of device I05, operates to reduce the control point of device 51 and thereby require sufiicient additional cooling to cause coil 45 to operate below the dew point of the air passing through it whereby moisture is removed by condensation, hence the air passing to the zone has less total moisture content by the amount of moisture condensed out. The additional cooling provided in duct I8 will also tend to cause a lowadded- 83? mixing dampers to permit an increased now of heated air, and thereby cause an increase in the temperature of said heated air, to maintain the temperature in the zones at the desired value This increase in heat in duct I6 at the sametime that air is being cooled in duct I8 is analogous to reheat in the conventional air conditioning sys-' tem and the system operates to keep the relative humidity below the limiting value for which device I is set. I

Under favorable circumstances, such as'in installations having blowers with a substantially constant volume output, only oneof connections it or I9 may be used for regulator I2, on the theory that any change in volume in-one'duct will be reflected in an opposite change of the same amount in the other duct. However, because of fluctuations in blower" capacity and becausethe difference in pressure between the ducts varies twice as much as the change in one duct, the arrangement shown is preferred. Also, instead of tubes I8 and 19 having their" ends turned downstream, with lateral openings to'respond to static pressure only, they may have open ends, turned upstream as shownin Figure 2, to respond to the difference-of dynamic pressures.

While the apparatus of Figure 1 includes 'a differential pressure responsive device for resetting thermostats 5i andB'I; it isobviou's that the difference in static pressure is'due 'to the difference in rate of flow in' the respective conduits. With this in mind, it is apparent that differential velocity responsivejmeans maybe substituted for the differential pressure responsiv'ej means; such a modification being shown-in Figure 3. Inthis fi ure; the dynamic pressure connection I2 I of Pitot tube I22 is connected to "a -bellows- I23+and thestatic pressure connection- I24 from Pitottube I22 "is connected to bellows I25 arrangedopposition to bellows" I23 and connected by a link 32 6 having a pivotbonnection I2 1. A- similar Pitot tube I32 is arranged in 'condui-t IB-f-and-its dynamic pressure conduit; I-3I isconne'c'te'dto" a bellows I33 while the static presjsureconduit I34 is connected to' bellows I35, this bellows being arranged in opposition to' I33a-nclf connected to the sameby a link I36 having a pivot connection I3l; A T-shaped member I39 having acrossbar extending through the'pivot connections I-2"I' and I 31 is arranged with its stem porti n insock'etI 4 I of bell crank lever I142 rotatable about a pivot i it? for adjusting valve plate BIrelative to nozzle 23. With this arran'gement, when the velocities in ducts It and I8 .are the same,,tl1e pressuresexerted by the dynamic pressure'bellows- I23 and I33 are'equal and the opposing pressure s-exerted by static pressure bellows I 25am I35; respec tively, are likewise equal, hence" T member I 42 may shift back or forth but therefli no= twisting of this member, hencebell crank I4;2 remains sta-' tionary. However, should theldi fference it'l -forces exerted by bellows I23 andbellows l25 exceed the difference in pressure between bellows I33 and I35, due to a higher 'air'veloc'ity indu'cflIIi than induct I8, link I26 will tendt'o' be pushed'further tothe left than willlink?I3Bfltherebyzcahsinga rotative movement of':T-member':I'3'9 iand= a' consequent rotation of bell crank I42-in'1a direction to lower valve plate 8| against nozzle-83 and thus cause an increase in the resetting-pressure. The increase in the resetting pressure dueto-a -rela-' tively greater velocity induet- Ifithanin'duct- 13 a is similar to the control action described above.

Because the static pressure ina'ducttehds torise as the dynamic pressure decreases, the difference in such pressures; and thus the response to veloc ity changes, is made more pronounced by the arrangement of Figure 3A- wherein static pressure bellows I25- opposes static pressure bellows I35 and dynamic pressure bellows-1123' opposes dynamic pressure bellows I33 With this arrangement, an increase in velocity in' duct I6 causes an increased dynamic pressurein bellows i23-anda decreasedstatic pressure in bellows I25, while the decreased velocity in duct I8r'esults in a decreased dynamic pressure in bellows" I33'and an increased static'pressure in bellows I35; thus causing a motion of T -member I 39 in a direc-'- tion to close nozzle'fliandfincrease the resetting pressure. Likewise, a higher velocity in duct. I8 than in IEiwill cause amovement of member I39 in a direction to decrease theresetting pressure. Thus, as pointed'out above', instead of resetting control1ers'5I and 5"! iii response to differential pressure, differential velocities" may be used instead.

Likewise", the resetting pressure may be connone-d as a function orth velocity in one duct, as shown in Figure 4, wherein P'ltdt tube I His 10- cated in duct It'ahd is connectedto bellows I23 and me; as before. nenows' maria-I25 are eon nected by a link IQB Which' intiilh connected to a pivoted lever I29 biased in a jnoz z leopening direction by a lightspring-f I30. The upperend of lever I29 isarranged to engage the underside of nozzle plate arm a direction toopen; nozzle 23 when the velocity du'ct IB is low and to close said nozzle when a predetermined high-velocity is reached, tube being'connected for resetting devices 51am 5'! in the same manneras above.

A simpler form of difierer'itial velocity control apparatus is" shown in Figure 5 wherein a vane I5I isattached to a crank lever I52 arranged in ductlfi'and a similar vane I53 carried by a crank lever I54 is arranged induct I8. Sockets I55 and IE6 of-levers I52 and I54, respectively, receive the crossbar I49 of If-member I39 and, upon avariation in velocity in ducts I6 andi8 whereinth'e velocities rise and fall equally, T-member I39 is merely shifted back and forth insocket I4I of bell crank I42, bell crank I42 remaining station ary. However, upon the velocity induct I6; for instance, exceeding that; induct I8; vane I51 is pivoted more than I53 thus-pausing a twistingof T-member I39 and a consequent rotation of bell crank- I42 in a direction to permit nozzle plate8'l' to move closer to nozzle 83; as above? Thus,'an increasenrvelocity in duct It results in a higher resetting pressure and-thus highercontrol points for thermostats-5i and" 51. Obviously; a single vane may be-used to control the resettingpres sureby arranging it to actuate a valve operating lever such-asl29in Figure 4:

Referring to Figure 6', the diifere'ncesun" air velocities I in ducts I6 and I S inay also be sensed by pivoted vanes" I 5 I' and I533" as above; or" other suitable velocityresponsive" means; carried by crank arms-I6 I and I763yrespec-tivelwwhich carry" wipers I64 and I85 of -rheostats 'IEBand I5??? Rheostats I53 and I59 are connected to functionas a voltage dividingpotentiometer for control'-' linga proportioning motor |"'-Whl011' operates potentiometers 208 and-26c? Potentiometers 208 and 209 are connectedto operate,insequence as shown or simultaneously, proportioning motors 2 I0 and 262-.' Motor 2H} is arranged to' adjust, or reset, the settingof a proportioning temperature controller 2I3 by means of pinion 2H and rack 11 2I2, controller 2I3 having a bulb 2I4 respondin to the temperature in duct I8. Controller 2 I3 is connected, in cooperation with a humidity responsive controller 260, to control motor 249 of valve 241 in pipe 46 and thus control the flow of cooling fluid to coil 45. Likewise, potentiometer 209 is connected to control proportioning motor 262 which adjusts, by pinion 263 and rack 264, controller 265 having a bulb 266 in duct I6. Device 265 controls proportioning motor 268 of valve 242 in pipe 4| and thus controls the flow of heating medium to coil 40. Motors 2I0, 2'62, 249 and 268 are similar to I95 hence the following description of the operation of motor I 95 applies equally well to them.

vIn operation, upon energizing transformer I1 I, the controlcircuit for proportioning motor I95 is energized by the following circuit: secondary winding I10 of transformer I1I, wire I12, wire I13, wiper I14, the left hand portion of resistor I15, wire I16, winding I11 of balanced relay I18, resistor I80, wire I8I, resistor I61 of rheostat I59, wiper I65, wire I68, wire I89 and the other terminal of secondary winding I10. From wiper I14, a parallel circuit comprises the right hand portion of resistor I15, wire I82, winding I83 of relay I18, resistor I85, Wire I86, resistor I56 of rheostat I58, wiper I64 and wire I69 where this circuit joins with that above described. With the present apparatus energized and with the Wiper I14 in the middle of resistor I15 and rheostats I58 and I59 equally adjusted, there is equal current flow through windings I11 and I93 of relay I18 hence there is no operation of said re lay. If the air velocity in ducts I6 and I0, assuming that the blower is operating, now be varied equally, vanes I5I and I53 will be equally defiected and rheostats I58 and I59 will be equally adjusted, hence the control circuit of motor I95 remains in balance. I

A demand for more heat for the zones, reflected in an increase in air velocity in duct I6 results in a further deflection of vane I5I and movement of wiper I64 to the left across resistor I66, thereby diminishing the resistance in the circuit in cluding winding I83 of relay I18. Because of the diminished resistance in this branch of the circuit, the right hand leg of relay I18 is more strongly attracted, thereby moving relay switch blade I88 into engagement with contact I9l and causing an energizing of the field windings of motor I95 by the following circuit: secondary winding I10 of transformer I1I, wire I89, relay switch blade I88, contact I9I, wire I96, motor winding I91, wire I12 and the other end of secondary winding I10. At the same time, the other winding of the motor is energized from wire I96 through capacitor I98, winding I94 and wire I12 to the transformer. This will be recognized as a common energizing circuit for a two phase motor. Upon energizing the motor winding as above described, armature 205 is caused to rotate so that output shaft 206 is driven by armature 205 through gear train 201 in a direction to move wiper I14 to the left across resistor I15 and thereby rebalance the circuits through relay I18 by decreasing the resistance in the branch containing winding I11 and increasing the resistance in the branch including winding I83. Upon a ba1- ance in these branch circuits being attained, blade I88 is then moved out of engagement with contact I9I and armature 205 is stopped. At the same time that wiper I14 was moved to the left across resistor I15, potentiometer 209 was adjusted in a similar fashion to control motor 262 12 in a manner to raise the temperature setting for controller 265 and thus require a higher tem perature in duct I6. Controller 265 then controls motor 268 of valve 242 in a manner to control the flow of heating medium through pipe M to give the desired higher temperature, the controlling circuit including potentiometer 209 and motor 262 and the circuit between controller 265 and motor 268 being essentially the same circuit used for controlling motor I95 with the exception that a unitary potentiometer is used rather than the two rheostats connected to operate as a-potentiometer. Simultaneous with the adjusting of potentiometer 269, potentiometer 208' is likewise adjusted but, as shown, a movement tothe left of the wiper of potentiometer 208has no efiect on the balance of its controlling circuit because the left portion of this potentiometer comprises a contact bar, the right hand portion of potentiometer 209 similarly comprising acontact bar or slide portion. Obviously, potentiometers 208 and 209 can be entirely conventional so that both motors 262 and 2I0 will be simultaneousl adjusted by operation-of motor I95, with overlapping of the heating and cooling sequences being prevented by a judicious selection of the amount of reset and the initial control point adjustments, as described in-the embodiment of Figure 1.

Should there be a demand for more cooling instead of heating, as above described, and vane I53 thereby be deflected more than vane I5I, the resistance in the branch of the controlling circuit including winding I11 is diminished and the switch blade I88 of relay I18 engages contact I90 to thereby energize winding I94 of the motor directly from wire I93 and winding I91 is energized through capacitor I98, causing armature 205 to rotate in an opposite direction, this being a typical reversible two phase motor. The opposite rotation of armature 205 causes output shaft 206 to rotate in a direction to advance wiper I1 4 to the right across resistor I15 to thereby rebalance its controlling circuit and stop the motor 205. This direction of rotation has no effect on potentiometer 209 because the right hand portion of the same is a mere slide contact portion but the adjustment of potentiometer 208 is effective to control motor 2I0 to adjust controller 2I3 to a lower control point to thereby require more cooling for the air in duct I8. Controller 2I3, instead of being connected directly to motor 249, is connected through a double potentiometer of humidity responsive device 260 by a limit control or compensated circuit 248. With this circuit, so long as the relative humidity affecting device 260 is below a desired value, this device has no effect and controller 2 I3 regulates motor 249 in a manner to obtain morecooling by permitting more cooling medium to flow through pipe 46 to the cooling coil. However, upon the relative humidity rising beyond said-value, device 260 then further adjusts motor 249 to require additional cooling with the eventual result that the cooling coil will be operated below the dew point to condense out excess water, in a manner described in the embodiment of Figure '1'. In this event, the extra'cooling will tend to diminish the cooling demand in the zones and increase the heating demand with the result that the air velocity in duct I6 willincrease and that in I8 diminish, thereby causing the adjusting of controllers 265 and 2I3 to higher control points. However, because controller 2I3-is no longer in sole control of valve 249, the cooling will con- 13 tinue and the additional heat called for by controller 265 will thus serve as reheat.

As in the previous examples, under favorable circumstances, a single vane l5! induct [5 may be directly connected to wiper blade 2 of potentiometer 212, potentiometer 212 being connected by Wires i 69, I8! and I86 to control motor I9 5 in the same manner as above described.

Further, if desired, rheost-ats I58 and [-59, connected to operate as a voltage dividing potentiometer, or potentiometer 27 2, may be connected directly to motors 252 and 210 to operate them in parallel and may even be connected'to operate motors 2'68 and 249 in parallel, motors I95, 2-62, 2 l and controllers 265 and 213 being eliminated.

Because various other substitutions and arrangements readily appear to those skilled in the art, upon a study of the present specification and drawings, the present invention is to be defined only by the appended claims.

I claim as my invention? 1. In an air conditioning system for a plurality of zones, a pair of ducts 'for delivering tempered air to said zones, blower means for circulating air through said ducts, heater means for heating the air in one oi said ducts, cooling means for cooling the air in the other of said ducts, branch means for diverting. air from each of said ducts to each of said zones, mixing damper means for controlling each of said branch means for proportioning the flow of air delivered from each of said ducts to each of said zones, a submaster type thermostat in each of said ducts responsive to the temperatur of the air in said ducts for controlling, respectivey, the heater means and the cooling means, means responsive to the difference in static pressures in said. ducts for adjusting said submaster thermostats, apparatus responsive to relative humidity, and means connecting said apparatus in controlling relation to said of said zones, damper means for controlling each j of said branch means by adjusting therelative volumes of air delivered from each of said ducts through said branch means, thermostatic means responsive to the temperature of the air in sa d one ductonly downstream of said temperature changing means and connected in controlling relation to said temperature changing means,

and means responsive to the difierence in static and dynamic pressure in at least one of said ducts for midifying the controllong relation between said thermostatic means and said temperature changing means.

3. In air conditioning apparatus for a plurality of zones, a pair of ducts for delivering air to said zones, blower means for circulating air through said ducts, temperature changing means for the air in at least one of said ducts, zone branch means for diverting air from each of said ducts to each of said zones, damper means for controlling each of said branch means by adjustmg the relative volumes of air delivered from each of said ducts through aid branch means, pivoted vane means located in at least one of said ducts and movable in response to air velocity, and control means actuated by said pivoted means con- 14 nectedin controlling relation tosaid temperature changing-"means;

4. In an air conditioning system for a plurality of zones, a pair of ducts for delivering tempered air to said zones, blower means for circulatin air through said ducts, heatermeans for heating the air inv one of said ducts, cooling means for cooling the airin the other of said ducts, branch means for diverting air from each of; said ducts to each of said zones, mixing damper means for controlling saidbranch means iorproportioningrelative volumes of air delivered from each} of said ducts to each of said zones, a submaster typethermostat in each of said ducts responsive to the temperature of the air in said ducts for controlling, respectively, the heater means and the cooling means, means responsive to the difference in air velocity of the air flowing in each-0f said ducts for adjusting said submaster type thermostat, apparatus responsive to relative humidity, and means connecting said apparatus in controlling relation to said cooling meansin a manner to exercise control of said cooling means when said relative humidity exceeds a predetermined value.

5. In an air conditioning system for a plurality of zones, a pair of ducts for delivering tempered air to said zones, blower means for circulating air through said ducts, heater means for heating the air in one of said ducts, branch means for diverting air from each of said ducts to each of said zones, mixing damper means for controlling each of said branch means for proportioning the air delivered from each of said ducts to each of said zones, 2. submaster type thermostat responsive to the air temperature in said one duct and connected in controlling relation to said heating means, said thermostat including an adjusting motor, and movable means responsive to the difference in air velocity in said ducts for operating said motor and thereby adjusting said submaster type thermostat in a manner to increase the heating effects of the air in said one duct when the air velocity in said one duct exceeds that in the other duct and to decrease said heating when the velocity of air in said otherduct is the higher.

6. In air conditioning apparatus for a plurality of zones, a pair of ducts for delivering air to said zones, blower means for circulating air through said ducts, cooling means for the air in at least one of said ducts, zone branch means for diverting air from each of said ducts to each of said zones, damper means for controlling each of 'said branch means by adjusting the relative volumes of air delivered from each of said ducts to said branch means, means movable in response to the difierence in air velocity in said ducts, control means operated by said movable means and connected in controlling relation tosaid air cooling means, and means responsive to relative humidity connected in a manner to assume dominating control of the controlling connection between said velocity responsive means and said cooling means.

'7. In an air conditioning system for a plurality of zones, a pair of ducts for delivering tempered air to said zones, blower means for circulating air through said ducts, temperature changing means for tempering the air in one of said ducts, zone branch means for diverting air from each of said ducts to each of said zones,

damper means for controlling each of said branch means for adjusting the relative volumes of air delivered from each of said ducts through said 15 branch means, and means disposed in the path of air flow of at least one of said ducts responsive to the velocity of the air being delivered by said duct connected in controlling relation to said temperature. changing means.

8. In' an air conditioning system for a plurality of zones, a pair of ducts for delivering tempered air to said zones, blower means for circulating air through said ducts, heater means for heating the air in one of said ducts, cooling means for cooling the air in the other of said ducts, branch means for diverting air from each of said ducts to each of said zones, mixing damper means ,for controlling each of said branch means for. adjusting the relative volumes of air delivered from each of said ducts to each of said zones, a submaster type thermostat in each of said ducts responsive to the temperature of the air in said ducts for controlling the heater means and the cooling means, means responsive to the relative air volumes being delivered by said ducts for adjusting said submaster thermostats, apparatus responsive to relative humidity, and means connecting said apparatus in controlling relation to said cooling means in a manner to exercise control of this cooling means when the relative humidity varies beyond a predetermined value.

9. In air conditioning apparatus for a plurality of zones, a pair of ducts for delivering tempered airto said zones, blower means for circulating air through said ducts, temperature changing means in at least one of said ducts, zone branch means for diverting air from each of said ducts to each of said zones, damper means for controlling each of said branch means by adjustingthe relative volumes of air delivered from each of said ducts to said branch means, thermostatic means responsive to the temperature of the air in said one duct only and located a short distance downstream of said temperature changing means and connected in controlling relation to said temperature changing means, and means responsive to the relative volumes of air passing through said ducts connected to said thermostatic means in a manner to adjust the controlling connection between said thermostatic means and said temperature changing means.

10. Control apparatus for a double duct air conditioningsystem comprising, in combination, a plurality of temperature responsive control devices located in said ducts and adjusted to respond to relatively high and low temperatures respectively, motor means for adjusting each of said devices, a plurality of devices responsive to air velocity in said ducts, means connecting said plurality of air velocity responsive devices in controlling relation to the motors of said temperature responsive devices for adjusting said temperature responsive devices in response to differences in air velocity, and means responsive to relative humidity connected in controlling relation to the motor of the temperature responsive device adjusted to respond to the relatively low temperature.

11. In air conditioning apparatus for a plurality of zones, a pair of ducts for delivering air to said zones; temperature changing means in one of said ducts, zone branch means for diverting air from each of said ducts to each of said zones, means for controlling the flow of air through said branch means, pivoted means located in each of said ducts and movable the direction of air flow in each of said ducts for responding to the velocity of air flow in said ducts, and means responsive to the difference in movement of said pivoted means for controlling said temperature changing means.

12. In air conditioning control apparatus for a double duct system having a temperature changing means in one of said ducts, air velocity responsive means for at least one of said double ducts, motor operated means for proportionally controlling said temperature changing means, an electrical network circuit for proportionally controlling said motor means, and means operable by said velocity responsive means for altering the balance of said network circuit and thereby adjusting the controlling relation between said network and said motor.

13. In air conditioning control apparatus for a double duct system, a control device having a shiftable throttling range constructed and arranged for proportionally controlling a motor, a pair of members each located in a different one of the above ducts and movable in response to air velocity in the ducts, and means connecting said members to said device for shifting the throttling range of said device in response to diiferences in the movements of said members.

FRANK R. FITZGERALD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,183,874 Shivers Dec. 19, 1939 2,210,868 Larson Aug. 6, 1940 2,254,185 Newton Aug. 26, 1941 2,363,595 Joesting Nov. 28, 1944 2,440,052 Lingen et a1. Apr. 20, 1948 2,495,861 Newton Jan. 31, 1950 

